Bill Gates ... the Microsoft founder could well have $17 billion less than Hosni Mubarak. Photo: Reuters

Former Egyptian President Hosni Mubarak is likely the world's richest man, with an estimated fortune of $US70 billion ($70.07 billion).

Mubarak's family fortune could be as high as $US70 billion, much of it in Swiss banks or tied up in real estate in New York, Los Angeles and London, media reported.

The $US70 billion would put the 82-year-old comfortably ahead of Mexican business magnate Carlos Slim Helu, worth about $US53.5 billion, and Microsoft founder Bill Gates, the richest American with $US53 billion.

According to Princeton political science professor Amaney Jamal, quoted by the ABC network in the US, Mubarak's three-decade rule in Egypt had kept him in a perfect spot to get a piece of any government action.

Mubarak, his wife and two sons were able to also accumulate wealth through a number of business partnerships with foreigners, Christopher Davidson, professor of Middle East Politics at Durham University in England, told ABC. Egyptian law requires that foreigners give a local business partner a 51 per cent stake in most ventures.

Meanwhile, Egyptian press reported that investigators were looking into the hidden wealth of Mubarak's allies, which ranged from the $US3 billion of party insider Ahmed Ezz to the $US1.2 billion of former interior minister Habib Ibrahim El-Adly.

Five hated cronies of Mubarak each amassed fortunes topping $US1 billion, according to military prosecutors preparing criminal cases against them in the latest government concession meant to defuse the two-week-old Egyptian crisis.

Three of them, former Cabinet ministers, tried to flee the country over the weekend but were denied permission, Cairo airport sources told Al-Masry Al-Youm, Egypt's largest independent newspaper.

"There was a lot of corruption in this regime and stifling of public resources for personal gain. This is the pattern of other Middle Eastern dictators," Princeton's Jamal told ABC News.

Protesters have cited government corruption as a reason they are demanding Mubarak's ouster.

Mubarak's family wealth reportedly dates back to when Mubarak was an air force officer and in a position to benefit from corporate corruption on military contracts, mainly through business partnerships with foreign investors.

Jamal told ABC that Mubarak's assets are most likely in banks outside of Egypt, possibly in the United Kingdom and Switzerland.

"This is the pattern of other Middle Eastern dictators so their wealth will not be taken during a transition, she said. "These leaders plan on this."

Meanwhile, Cairo tried to shore up one of its biggest sources of support - Egypt's civil service - on Monday, by announcing a 15 per cent pay hike for six million government workers.